VERFAHREN UND GERAET ZUR AUTOMATISCHEN KORREKTUR EINES SUBTRAKTIONSBILDES.

摘要

In a temporal subtraction processing conducted by use of stimulable phosphor sheets, the difference between maximum transmitting radiation amount of digital image signals detected from the stimulable phosphor sheets carrying radiation images stored therein is calculated. The difference is added to a difference signal obtained by the subtraction processing prior to a gradation processing, or a gradation conversion table is shifted by the difference towards the high density side along the input signal coordinate axis. Or, read-out conditions in final read-out are adjusted so that the difference is eliminated. Or, a maximum frequency point signal is calculated from a histogram of the difference signal, the difference between a signal representing the standard background density of a subtraction image and the maximum frequency point signal is calculated, and correction is made so that the background density in the subtraction image becomes always the same.